Tap changer with sequential contact actuating means



April 4, 1967 I D. WHITE 3,312,793

TAP CHANGER WITH SEQUENTIAL CONTACT ACTUATING MEANS Filed March 24, 1965 e Sheets-Sheet 1 FIG.|B.

INVENTOR Dole White ATTORNEY April 4, 1,967 N i D. WHITE 3,312,793

TAB CHANGER WITH SEQUENTIAL CONTACT ACTUATING MEANS File d March 24, 1965 6 Sheets-Sheet 2 April 4, 1967 D. WHITE 3,312,793

TAP CHANGER WITH SEQUENTIAL CONTACT ACTUATING MEANS Filed March 24, 1965- 6 Sheets$heet 5 VABLE TAP SELECTOR 44 MOVABLE TAP SELECTOR 46 D. WHITE A ril 4, 1967 TAP CHANGER WITH SEQUENTIAL CONTACT ACTUATING MEANS Filed March 24, 1965 6 Sheets-Sheet WHITE 3,312,793

TAP CHANGER WITH SEQUENTIAL CONTACT ACTUATING MEANS April 4, 1967 Filed March 24, 1965 6 Sheets-Sheet 5 D. WHITE April 4, 1967 TAP CHANGER WITH SEQUENTIAL CONTACT ACTUATING MEANS Filed March 24, 1965 6 Sheets-Sheet 6 United States Patent TAP CHANGER WITH SEQUENTIAL CONTACT This invention relates in general to load tap changers for electrical inductive apparatus, and more particularly to load tap changers of the resistive type.

Under load tap changer systems of the resistive type, wherein resistor means is utilized to reduce the magnitude of current flow during the transition period when two adjacent winding taps are both electrically connected in the circuit, commonly utilize transfer switches of the overcenter toggle mechanism type. This type switch usually has three linkingmembers pivotally connected end-to-end,

with the outer ends of the outer links pivotally connected to fixed points spaced to allow the inner link to align itself with either outer link. A spring member is attached to the inner link and to a movable carriage, which moves between the fixed ends. The spring holds the inner link in alignment with one of the outer links until the carriage forces the aligned outer link out of alignment. The spring then pulls the inner link into alignment with the other outer link. In order to switch from one tap on a tapped winding to another, under load, two transfer switches are required, usually disposed in spaced superposed relation, and they must operate in sequence, with first one switch changing its position or switching, and then the other. Sequencing of toggle mechanism type transfer switches requires an additional linking member connected obliquely between the inner link member of the vertically disposed switches. This additional linking member must be of sturdy construction, and must be carefully aligned, as accurate sequencing depends upon the alignment of the additional linking member. This type of transfer switch generally has butt-type contacts, as the operation of the switch is not positive, depending entirely upon spring force action. Other types of contacts, such as contacts of the finger or knife blade type, may introduce delays into the switching sequence. Further, the fact that the operation of the switch is not positive, allows the switch to be driven by external means into switching when switching is not actually desired. Still further, this type switch has two movable contact carrying members, which reduces the clearance between the contacts, and adversely affects the interrupting capacity of the switch.

Accordingly, it is an object of the invention to provide a new and improved load tap changer of the resistive type, for electrical inductive apparatus.

Another object of the invention is to provide a new and improved transfer switch assembly for use with load tap changers.

A further object of the invention is to provide a new and improved transfer switch assembly for load tap changers which is positive in its operation.

Another object of the invention is to provide a new and improved transfer switch arrangement for load tap changers in which a substantially vertical, lightweight, connecting member between vertically disposed switching portions may be utilized to accurately sequence the switching operation.

Still another object of the invention is to provide a new and improved transfer switch arrangement for load tap changers in which accurate alignment of the switches is not required in order to provide accurate sequence switching.

Still another object of the invention is to provide a transfer switch for load tap changers, in which the mov- 3,312,793 Patented Apr. 4, 1967 "ice able contacts of each switching portion are carried by a single contact carrier.

Another object of theinvention is to provide anew and improved transfer switch for load tap changers in which there is no power flow through the mounting base of the switch and associated bearings.

Briefly, the present invention accomplishes the above cited objects by utilizing a spring and latch arrangement in which energy is stored in the spring only after the load tap changer has received a signal to switch the electrical circuit to another tap, and the switching is prevented from occurring until a predetermined amount of energy has been stored in the spring, by a latch and latch wheel arrangement. A lightweight, vertically disposed, insulating rod is connected from the latch wheel of one switch to the latch wheel of the second switch which is disposed in spaced vertical relation with the first switch, to control the sequencing of the switches. The alignment of the switches is not critical, as the vertical distance between the switches, which can be easily predetermined and fixed, is the only factor affecting the delay time between the switching of the switches.

The switching operation is positive, with the moving contacts being forced to complete their travel by positive c'amming means.

The mounting base of the transfer switches is at the same potential as the movable contact carrier, with insulation disposed to prevent power flow from the mounting bases and bearings associated therewith to any portion of the electrical circuit.

Further objects and advantages of the invention will become apparent as the following description proceeds and features of novelty which characterize the invention will be pointed out in particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the invention, reference may be had to the following detailed description taken in connection with the accompanying drawings, in which:

FIGURES 1, 1A and 1B are schematic diagrams illustrating a transformer having a tapped winding section and a load tap changer arrangement of the resistive type;

FIG. 2 is an elevational view of a transfer switch arrangement constructed according to the teachings of the invention;

FIGS. 3 and 3A are elevational and fragmentary views, respectively, illustrating certain portions of a transfer switch constructed according to the teachings of the invention;

FIG. 4 is a plan view of the transfer switch shown in FIG. 3; and

FIGS. 5A and 5B are elevational views of a transfer switch assembly, which illustrate still other portions of a transfer switch assembly constructed according to the teachings of this invention, and means for sequencing the operation of the transfer switch.

Referring now to the drawings, and FIG. 1 in particular, there is illustrated a schematic diagram of a threephase transformer 10 of the autotransformer type, having line terminals 12, 14 and 16 for connection to a source of alternating potential (not shown), and terminals 13, 2t) and 22 for connection to a load circuit (not shown). In general, transformer 10 has phase winding portions 24, 26 and 28, each including a high voltage section 30, a low voltage section 32, a tapped section 34 having a plurality of taps such as T1, T2, T3, T4, T5, T6, T7, and T8 and means 36 for adjusting the voltage which appears at the low voltage terminal 18. Since the winding portions and voltage adjusting means for each of the phase winding portions 24, 26 and 28 are similar, only the winding sections and voltage adjusting means for phase winding portion 24 are shown in FIG. 1.

Means 36 for adjusting under load the voltage which appears at terminal 18, includes a selector switch 38 for selecting the various taps on tapped winding section 34,

a reversing switch 40 for reversing the polarity of tapped winding section 34, and transfer switching means 42.

The selector switch 38 may be of the type which has stationary contacts disposed in two concentric circles, with one circle of contacts being connected to the even numbered taps on tapped winding section 34, and the other circle of contacts being connected to the odd numbered taps. The selector switch 38 has two movable contacts 44 and 46, which contact the stationary contacts. Movable contact 44 moves in the circle of odd numbered contacts, and movable contact 46 moves in the circle of even numbered contacts. The movable contacts 44 and 46 of selector switch 38 are connected to transfer switching means 42, and are suitably interlocked to allow only the movable contact not connected in the circuit by transfer switching means 42, to break connection with one of the taps on tapped winding section 34. The reversing switch 40 is a single pole, double throw switch, having stationary contacts 48 and 50 connected to the ends of tapped winding section 34, and a movable contact 52 connected to winding section 30 and a stationary contact 54 in selector switch 38. The reversing switch 40 is suitably interlocked to allow it to be operated only when movable contact 46 of selector switch 38 is connected to stationary contact 54 and to the terminal 18, through transfer switching means 42. Thus, tapped winding section 34 is removed from the circuit when the reversing switch 40 is operated. Transfer switching means 42 includes two single pole,

' double throw switching portions 60 and 70. Transfer switch portion 60 has stationary contacts 62 and 64, and a movable contact 66. Transfer switch portion 70 has stationary contacts 72 and 74, and a movable contact '76. Resistance means, illustrated by resistor 80, is connected between the two movable contacts 66 and 76 of transfer switch portions 60 and 70, respectively.

FIGS. 1, 1A and 1B illustrate the operational sequence of transfer switching means 42. Referring to FIG. 1, movable selector switch contact 44 is connected to tap T3 of tapped winding section 34, and to terminal 18 through stationary contact 62 of transfer switch portion 60. Movable contact 44 is also connected to terminal 18 through stationary contact 72 to transfer switch portion 70 and resistance means 80, but due to the relative impedances of the two parallel circuits, most of the current will flow through transfer switch portion 60. It will be noted that movable selector switch contact 46 is not connected in the circuit, and is free to move to the even numbered tap T4. When the regulating circuit associated with the transformer 10 calls for a voltage change, movable tap selector contact 46 will move to tap T4, or stay on tap T2, depending upon whether the line voltage is to be increased or decreased. Assume that tap selector contact 46 remains on tap T2. The first step in the switching process is shown in FIG. 1A, with transfer switch portion 60 moving its movable contact 66 from stationary contact 62 to stationary contact 64. During the short interval of time that movable contact 66 is moving between stationary contacts 62 and 64, the circuit will be established through contacts 72 and 76 of transfer switch portion 70 and resistance means 80. As soon as movable contact 66 of transfer switch portion 60 makes contact with stationary contact 64, the circuit will be established through both taps T2 and T3, with resistance means preventing a short circuit and excessive current flow due to the circuit being established across two adjacent taps on tapped winding section 34. When transfer switch portion 60 has established a new circuit through its contacts 64 and 66, transfer switch portion 60 causes transfer switch portion 70 to switch, and establis'h a circuit through its contacts 74 and 76, thus breakwith both transfer switch portions 60 and 70 being connected to tap T3, and ending with both transfer switch portions being connected to tap T4. Movable selector contact 44 is now free to move totap T1 if the system requires a still greater voltage change in the same direction.

The transfer from one tap to the next has been made without interrupting power flow to the load circuit, and

without damaging the tapped winding section 34 when adjacent taps are both electrically connected in the circuit.

Since transfer switching means 42 must stand up under repeated switching operations and provide continuous current carrying duty without excessive losses and damage to its contacts and operating structure, and also must provide the desired accurate sequencing of the switching of transfer switch portions 60 and 70, the

construction of switching means 42 is of vital importance.

It should be positive in operation, preventing operation of its switching portions unless switching is actually called for. It should have a rugged, low-loss contact structure, which will carry the load current continuously without excessive heating and pitting of the contact structure. It should prevent current flow through its base structure and associated bearings, thus eliminating any pitting and possible freezing of the bearings, and, it

should have a simple but effective sequencing means for operating the switches, which does not require elaborate alignment of the switches and critical alignment of interconnecting actuating members.

FIG. 2 is an elevational view of a transfer switching means constructed according to the teachings of the invention, which possesses all of the hereinbefore stated advantages, with like reference numerals in FIGS. 1 and 2 indicating like components.

More specifically, FIG. 2 illustrates a general outline of transfer switching means 42, showing the basic components and their relative locations. Transfer switching means 42 is dis-posed within a suitable tank or enclosure 82, which is filled to a predetermined level 84 with a suitable fluid dielectric, such as oil. Transfer switching means 42 includes two transfer switching portions or switching decks 60 and 70 which are disposed in spaced, superposed relation by four insulating rods or members 86, which are suitably connected to the top of the enclosure 82 and to the mounting bases 88 and 90 of switch ing portions 60 and 70, respectively.

Suitable driving means (not shown) such as an electric motor, supplies torque to miter gear drive 92 through suitable gearing means 93, in response to a signal from voltage regulating means (not shown) when it is desired to change tap connections.

A crank member 94, connected to the output shaft 9 6 of miter gear drive 92, provides motion to connecting rod member 98, which is formed of a suitable electrical insulating material. Connecting rod member 98 has its outer'ends connected between crank member 94 and crank member 100, the latter being associated with transfer switching portion '60. Crank member 100 is connected to drive shaft 102 of transfer switching portion 60 and crank member 104 is fixed to drive shaft means 102.

Crank member 104 rotates in response to motion imparted to drive shaft 102 by crank member 100 and connecting rod 98.

Transfer switch portion 60 has a single movable contact carrier assembly 106 pivotally disposed on shaft member 108, which moves between stationary contact assembly 110 and stationary contact assembly 112. Energy storage means, such as spring package 114, is connected between movable contact carrier assembly 106 by shaft member 116, and crank member 104 by shaft member 118, and provides the force or stored energy for switching movable contact carrier assembly 106 from one stationary contact assembly to the other. One functionof crank member 104 is to extend spring package 114 in response to a requirement for switching, to ready the transfer switch portion 60 for the switching operation. When spring package 114 is extended, a plurality of springs 115 are compressed as shown in the partially cut-away view of spring package 114.

Transfer switch portion 70 has a crank member 120, which is similar in configuration to crank member 104 of transfer switch portion 60, fixed to a shaft member 122. Transfer switch portion 70 also has a single movable contact carrier assembly 124 pivotally disposed on shaft member 126, stationary contact assemblies 128 and 130, and a spring package 132 connected between movable contact carrier assembly 124 at shaft1'34, and crank member 120 at shaft 136. Crank member 104 of transfer switch portion 60 is interconnected with crank member 120 of transfer switch portion 70 through a connecting rod member 138, formed of a suitable electrical insulating material, with the ends of connecting rod member 138 being pivotally connected to shafts 140 and 142, which are fixed to crank members 104 and 120, respectively. Thus, when rotary motion is imparted to crank member 104 through drive shaft 102, rotary motion is also imparted to crank member 120 through connecting rod member 138, compressing both spring packages 114- and 132, simultaneously. When transfer switch portion 60 is switched, transfer swith portion 70 is made responsive to the switching of transfer switch portion 60 through a connecting rod member 144, formeds of a suitable electrical insulating material, which interconnects the two switching portions in a substantially vertical manner, as will be hereinafter explained.

Suitable static rings, such as rings 146, 14 8 and 150, formed of a suitable electrical conductor, may be disposed in spaced axial alignment with the vertical center line of transfer switching means 42, to reduce the voltage gradient. Static ring 146 may be connected to ground or to the frame of drive 92, and static rings 148 and 150, which are disposed to enclose transfer switching means 42, may be electrically connected to transfer switch portion 60, and electrically insulated from transfer switch portion 70.

FIGS. 3 and 4 illustrate elevational and plan views, respectively, of the contact arrangement and structure of one of the transfer switch portions, such as transfer switch portion 60. Since the contact structure of both transfer switch portions 60 and '70 is similar, only the contact structure of transfer switch portion 60 will be described.

In general, transfer switch portion 60 is a single pole, double throw switch, having a single movable contact carrier 106 which carries contact members 107, 109, 111 and 113, and two similar stationary contact assemblies 110 and 112. Each stationary contact assembly has two stationary contact members such as stationary contact members 162 and 164 on stationary contact assembly 110, for receiving movable contact members 111 and 113, respectively, and stationary contact members 163 and 165 for receiving movable contact members 107 and 109, respectively. Since the two stationary contact assemblies 110 and 112, are similar, only stationary contact assembly 110 will be described in detail.

Also, each transfer switch may have one or more single pole, double throw portions, connected in parallel, such as portions 156,158 and 160, as shown in FIG. 4, with the number of parallel connected portions being determined by the current rating of the particular transfer switch. Since each single pole, double throw portion of the transfer switch is similar to the other portions, only one will be described in detail.

Transfer switch portion 60 includes a main mounting base member 88, upon which stationary contact assemblies 110 and 112 and movable contact carrier assembly 106 are disposed. Stationary contact assembly 110 comprises a main'contact supporting structure 152, supported by main mounting base member 88 through electrical insulating means, such as electrical insulating member 154. The main contact supporting structure holds 'and breaking of the contacts is accomplished by the relative positions of stationary contacts 162 and 164 with respect to movable contacts 111 and 113.

Arcing contacts 164 are supported by arcing contact mounting assembly 166, which is mounted on main contact mounting assembly 152 by suitable mounting means,

such as bolt 168. An insulating washer member 170, an 'insulating tubular member 1'72, and an insulating sheet member 174, are utilized to electrically insulate the arcing contact mounting assembly 166 from the main contact mounting assembly 152.

The arcing contact mounting assembly 166 is electrically insulated from the main contact mounting assembly 152 in order to direct the current flowing in the arcing contacts 164 into current balancing means 180. As hereinbefore stated, a plurality of single pole, double throw switch portions are connected in parallel to provide the desired current carrying capacity, such as portions 156, 158 and 160, shown in FIG. 4. Balancing means is utilized to balance the current flowing in the plurality of parallel connected arcing contacts, in order to equalize the burning of the arcing contacts. The balancing means 180 is connected to the individual arcing contacts through electrical conductors 1'82, 184 and 186, and the output of balancing means 180 is connected in common to main contact mounting assembly 152 at member 188. Main contact 162 is electrically connected to member 188 through main contact mounting assembly 152, and arcing contact 164 is connected to member 188 through arcing contact mounting assembly 166 and balancing means 180. Member 188 is connected through suitable electrical conductor means to one of the movable tap selectors on tap selector switch 38, such as to tap selector 46 (see FIG. 1). The corresponding member 190 on stationary contact assembly 112 would then be connected to the re maining movable tap selector contact, such as selector contact 44.

Movable contact carrier assembly 106 is electrically connected to one end of resistance means 80 (see FIG. 1), and also to line terminal 18, in the case of transfer switch portion 60. This connection from movable contact carrier assembly 106 to resistance means 80 is made through bus 192.

Movable contact carrier assembly 106 is free to pivot about shaft 108, and thus the electrical connection from the movable contact carrier assembly 106 to bus"192 must be flexible. The main mounting b-ase88 is thus electrically connected to the potential applied to movable contact carrier assembly through shaft 108. Therefore, it is necessary to prevent a current path from being established through the main mounting base 88 to bus 192, in order to prevent current flow through the various bearings associated with the mounting base, which could cause arcing, pitting and possible freezing of the bearings. FIG. 3 illustrates how the bus 192 may be mounted on the main base assembly 88, in an insulating manner. The bolt 194 for securing bus 192 to the main mounting base 88 is electrically insulated from the bus 192 by insulating washer member 196, and insulating tubular member 198. The bus 192 may be electrically insulated from base mounting member 88 by sheet insulating member 200.

FIG. 3A is a fragmentary view illustrating how movable contact carrier assembly 106 may be connected to bus 192 with a flexible conductor 202. Flexible conductor 202 may be bolted to movable contact carrier assembly 106, such as with bolts 204 and 206, and may be connected to bus 192 by nut and bolt means 200 and 210. The base member 80 is cut-out, as shown at 2112, to allow the flexible conductor 202 to be connected to mounting base 192 without electrically contacting base mounting member 88. Thus, the only way for power to flow from the bus 192 to the movable contacts 107, 109, 111 and 113 is through the flexible conductor 202. Power cannot flow through base mounting member 08 and its associated bearing members, even though mounting base 88 is at the same potential as movable contact carrier assembly 106. It is important to note that all of the movable contacts 107, 109, 11 1 and 113 are carried by a single contact carrier 106, which provides maximum clearance between stationary and movable contacts when the switch is operated.

FIGS. A and 5B are elevational views of transfer switching portions 60 and 70, respectively, illustrating means for effecting the switching of the transfer switch portions 60 and 70, and also the sequencing means for operating transfer switch portion '70 a predetermined period of time after transfer switch portion 60 is operated.

When shaft member 102 is turned counterclockwise by crank member 100 and connecting rod member 90 (see FIG. 2), crank member 104, which is fixed to shaft member 102, starts to extend the spring package 114, which is connected between movable contact carrier as sembly 106 at shaft 116 and an arm of crank member 104 at shaft 118. The movable contact carrier assembly is prevented from moving while the springs 115 in the spring package 114 are beingcompressed to a predeter mined amount of stored energy, by connecting rod member 214, which is pivotally connected to movable contact carrier assembly 106 at' shaft 216, and pivotally connected to latch wheel member 210 at shaft 220. Latch wheel member 218 is rotatably connected to fixed shaft 222. Latch wheel 210 is prevented from rotating clockwise by latch member 224, which is pivotally connected to shaft 226. The projecting finger 223 of latch member 224 engages a mating notch 228 on latch wheel 218, which is urged into maintaining this position by spring member 230, which is connected between latch member 224, and another latch member 232. Latch member 2232 is also pivotally connected to shaft 226, and is used to prevent counterclockwise movement of latch wheel 218, which will be hereinafter explained.

Thus, we have crank member 104 turning counterclockwise and extending spring package 114, which provides the stored energy for switching movable contact carrier assembly 106 from its position whereby its contacts 107 and 109 will break from engagement with stationary contacts 163 and 165, and move its contacts 111 and 113 into engagement with stationary contacts 162 and 164. Connecting rod member 214 prevents movement of the movable contact carrier assembly 106 while spring package 114 is being extended, as shaft 220 disposed on latch Wheel 218 is not free to move due to the latching finger 223 of member 224 engaging a depression or notch 228 on its outer surface. Crank member 104 also has a cam surface 234 disposed thereon, which rotates counterclockwise with crank member 104, and is located such that it engages latch member 224 after the spring package has been fully extended. The counterclockwise rotation of cam surface 234 extends spring member 230, rotating latching member 234 about its shaft 226, and pulling the projecting finger portion 223 of latch member 224 from engagement with the mating notch 228 on latch wheel 21%. Latch wheel 218 is then free to rotate about its shaft 222. With connecting rod member 214 no longer restrained by shaft 220, the stored energy in spring package 114 is released, quickly moving movable contact carrier assem-- bly 106 from the position shown in FIG. 5 to the opposite position, shown in FIG. 3. Dashpots, built into spring package 114, control the speed of the movable contact carrier 106. With fixed shafts 222 and 108 being linked, from shaft 222 to movable shaft 220 through latch wheel member 218, from movable shaft 220 to movable shaft 216 through connecting rod member 214, and from movable shaft 216 to fixed shaft through movable contact carrier assembly 106, When the contact carrier switches from the position shown in FIG. 5A to the opposite position, movable shaft 216 is pivoted counterclockwise, and shaft 220 is forced to move downward, thus rotating latch wheel 218 in a clockwise direction. Latch wheel 210 rotates clockwise until movable contact carrier assembly 106 stops, with its movable contacts 111 and 113 firmly engaging stationary contacts 162 and 164. Notch 236 is disposed on the outer surface of latch wheel 218, which moves clockwise with latch wheel 218. Notch 236 is disposed in a predetermined location which will correspond to the location of the projecting finger 231 of latch member 232. Thus, when latch wheel 218 stops rotating, spring member 230 will force finger 231 of latch member 232 to engage the mating notch 236 and lock latch wheel 218 in its new position.

The spring action of spring package 114 and the inertia of movable contact carrier 106 is such that the movable contacts will seat properly with the slotted stationary contacts, resulting in excellent electrical contact. This proper seating of the contacts assures that latch wheel 218 will rotate far enough to allow it to be locked by latch member 232. However, proper seating of the contacts and locking of the latch wheel 218 may be positively insured by utilizing crank member 240, which is pivotally fixed to shaft 242. Crank member 240 is linked with a projecting arm of connecting rod member 214, with linking member 244 being pivotally connected to connecting rod member 214 and crank member 240 by shafts 246 and 248, respectively. Crank member 104 has an additional cam surface 250 disposed thereon, which will engage a cam surface or roller 252 on crank member 240 if the movable contact carrier 106 has not moved into the proper position. Cam surface 250 will force crank member 240 to pivot counterclockwise about its shaft 242, causing linking member 244 to push shaft 220 further in a counterclockwise direction through connecting rod member 214, thus forcing the movable contact carrier assembly 106 to complete its travel, and moving latching wheel 210 into position where it will be locked by latch member 232. If the movable contact carrier 106 completes its prescribed travel upon its initial switching movement, cam 250 will not contact cam roller 252, as cam roller 252 will be moved outward, back to its initial position, due to the normal action of connecting rod member 214, and linking member 244.

When transfer switch portion 60 is switched from the position shown in FIG. 3 to the position shown in FIG. 5A, the operation of the switch is the same as hereinbefore described, except all directions will be opposite. Thus, crank member 104 will be rotated clockwise about shaft 102, again compressing the springs 115 in spring package 114, cam surface 254 and crank member 104 will engage latch member 232 after the spring package 114 is fully extended, allowing the spring force to move contact carrier 106 clockwise to the position shown in FIG. 5A, and latch wheel 218 is moved counterclockwise to allow latch member 224 to lock latch wheel 218 in notch 228. The positive follow through is similar, with cam surface 256 on crank member 104 engaging cam roller 252 on crank member 240 if the movable contacts have not fully seated. Due to the new position of shaft 220, however, movement of crank member 240, will, through linking member 244, cause shaft 220 to rotate further in a counterclockwise direction, instead of clockwise, causing the movable contact assembly to rotate further in a clockwise direction.

The coordination of'the switching of transfer switch portion 60 and transfer switch portion 70 will now be described. When shaft 102 is turned counterclockwise to initiate counterclockwise switching of movable contact carrier assembly 106, crank member 104 also turns crank member 260 about shaft 122 in a counterclockwise direc tion, through connecting rod 138, which is pivotally connected to crank members 104 and 260 by shafts 140 and 262, respectively. A spring package 132, pivotally connected between movable contact carrier assembly 124 and crank member 260, at shafts 134 and 136, respectively, is extended due to the counterclockwise rotation of crank member 260. Connecting rod member 262, latch wheel 264, and latch member 260 prevent movement of movable contact carrier assembly 124 while the spring package 132 is being extended, in a manner similar to that described for transfer switch portion 60. Connecting rod member 262 is pivotally connected to both latch wheel member 264 and movable contact carrier assembly 124 at shafts 266 and 268, respectively, with latch wheel 264 being rotatably fixed to shaft 270. Latch member 260, which is pivotally fixed to shaft 280, has a projecting finger 272 which engages a mating notch 274 in latch wheel 264, and is urged into locking engagement by spring member 276. Spring member 276 is connected between latch member 260, and latch member 282, which is also pivotally fixed to shaft 280, and is used to lock latch wheel 264 from traveling counterclockwise when movable contact carrier assembly 124 is in the position shown in FIG. 3. Transfer switch portion 70 also has means for assuring proper seating, similar to the means described relative to transfer switch portion 60, and it includes cam surfaces 284 and 286 on crank member 260, crank member 288 pivotally fixed to shaft 290, and linking member 292 pivotally connected between connecting rod member 262 and crank member 288 at shafts 294 and 296, re-

spectively.

Up to this point, the construction and operation of transfer switch portions 60 and 70 is similar. The major distinction is in the way transfer switch 70 is tripped. Instead of utilizing a cam surface 234 on crank member 104, as in transfer switch portion 60, transfer switch portion 70 is switched in response to the switching of transfer switch portion 60. This coordination is accomplished by connecting rod member 144. Connecting rod member 144 is an insulating rod disposed in a substantially vertical manner between the superposed transfer switch decks. Connecting rod member 144 may be of lightweight construction, since it doesnt have to overcome any great spring pressure, which is important because the rod is constructed of an electrical insulating material. Further, no elaborate alignment procedures are necessary between the switches. Connecting rod member 144 is not required to be disposed at any predetermined oblique angle between the switch decks, but is vertically disposed, with only the distance between the points of connection at its ends being important, which may be easily and accurately jig drilled.

More specifically, connecting rod member 144 has one end pivotally connected to latch wheel member 218 of transfer switch 60 at shaft 300, and its other end connected to linking member 302 at shaft 304. Linking member 302 includes two matching spaced portions disposed on the outside of latch members 260 and 282, with a shaft 304 disposed through the outer ends of the spaced portions. Linking member 302 has its other spaced ends pivotally fixed to shaft 280, which is the same shaft on which latching members 260 and 282 are disposed. Latching member 260 has a cam portion 306 disposedthereon, and latching member 282 has a cam portion 308. The shaft 304, to which connecting rod member 144 and linking member 302 are pivotally connected, acts as an actuating pin, since the portion of the shaft 304 between spaced matching portions of link member 302 will contact either cam 306 or cam 308 as it moves about fixed shaft 280.

When transfer switch portion 60 is in the position shown in FIG. A and it is tripped, latch wheel 218 is forced to move in a clockwise direction. This clockwise move- 10 ment of latch wheel 218 moves connecting rod member 144 in an upward direction, with shaft 304 striking cam portion 306 of transfer switch portion 70, a predetermined interval of time after transfer switch portion 60 has been switched, with the delay time being determined by the distance between shaft 304 and cam surface 306 of latch member 260. When shaft 304 strikes cam surface 306, projecting finger 272 is moved out of its mating notch 274, overcoming spring member 276, allowing transfer switch portion to switch. When transfer switch portion 70 has switched to the, position shown in FIG. 3, projecting finger 310 on latch member 282 will engage matching notch 312 on latch wheel 264, locking latch wheel 264 in its new position, with spring member 276 urging the parts into locking engagement.

When the transfer switch portions 60 and 70 are in the position shown in FIG. 3, and transfer switch 60 is switched, connecting rod member 144 will be moved in a downward direction, and will trip transfer switch portion 70 when shaft 304 strikes cam surface 308 on latch member 282. The delay in switching between transfer switch portions 60 and '70 is determined, in this instance, by the distance between shaft'304 and cam surface 308.

Thus, in summary, there has been disclosed a new and improved transfer switch for under load tap changers of the resistive type, which has many advantages over prior art transfer switches. There is a single movable contact carrier which carries all of the movable contacts, instead of separate carriers for each stationary portion of the switch. This is very important, as it provides a greater insulating clearance between the separated stationary and movable contacts, providing increased interrupting capacity. This feature also permits the use of greater amounts of material on the arcing contacts, providing longer contact life.

The switches are positive in operation, with no spring pressure urging switching until switching has actually been called for. There is no chance of the switch being forced into false switching by foreign or external means. It will only switch when the main drive shaft is actuated by a signal to switch.

Knife switch type contacts may be utilized, as proper seating is assured by positive follow through action of positively engaged parts, thus providing better electrical contact between the contacts than provided by butt type contacts, extending contact life. Further, butt type contacts, necessary on some prior art type switches, require that continuous spring pressure he applied urging them together, which spring pressure is also used to switch the transfer switch, which allows possible false switching if the movable contact structure is moved by some external means. i

The rugged switch structure is comprised of simply made parts, and the arrangement of the parts and insulating members assures there will be no power flow through the mounting members and associated shafts, preventing pitting and freezing of the bearings.

Still further, the coordinating means for sequencing the switching is simple but accurate. No elaborate alignment of obliquely disposed connecting members is required. Only two vertically disposed connecting rods are required. It is only necessary to set the vertical distance between the connecting points on the connecting rods, to assure accurate sequencing. No further close alignment of the switches is necessary.

Since numerous changes may be made in the above described apparatus and different embodiments of the invention may be made without departing from the spirit thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative, and not in a limiting sense.

I claim as my invention:

1. A transfer switch assembly for -a load tap changer comprising first and second switching means disposed in ing electrical contacts, and a single movable contact carrier having contacts, said movable contact carrier being pivotally disposed between said two stationary positions, first and second energy storage means for pivoting said movable contact carriers of said first and second switching means, respectively, means for storing energy in said first and second energy storage means when it is desired to switch the movable contact carriers of said first and second switching means from one stationary contact position to the other, first and second latching means associated with each of said first and second switching means, respectively, for maintaining the position of said movable contact carriers of said first and second switching means until switching is desired, means tripping said first latching means to allow said first switching means to switch when said first and second energy storage means have a predetermined amount stored therein, means responsive to the switching of said first switching means tripping said second latching means and allowing said second switching means to switch a predetermined period of time after said first switching means has switched.

2. A transfer switch assembly for a load tap changer comprising firs-t and second switching means disposed in spaced superposed relation, each of said first and second switching means having two stationary positions each having electrical contacts and a single pivotally disposed movable contact carrier having contacts, said movable contact carriers pivoting between said two stationary positions when said first and second switches are switched, to engage certain of its electrical contacts with the stationary electrical contacts at one stationary position and break certain of its electrical contacts with the contacts of the other stationary position, first and second energy storage means for pivoting said movable contact carriers on said first and second switching means, respectively, means for storing energy in said first and second energy storage means when it is desired to switch said first and second switching means, first and second latching means associate-d with each of said first and second switching means, respectively, for maintaining the position of said movable contact carriers of said first and second switching means until switching is desired, means for tripping said first latching means to allow said first switching means to switch when said first and second energy storage means have a predetermined amount of energy stored therein, means disposed in a substantially vertical manner between said first and second switching means responsive to the switching of said first switching means for tripping said second latching means and allowing said second switching means to switch a predetermined period of time after said first switching means has switched, first and second positive closing means associated with said first and second switching means, respectively, which assure that said movable contact carriers on said first and second switching means pivot a predetermined distance each time said first and second switching means are switched.

3. A transfer switch assembly for a load tap changer comprising first and second switching means disposed in spaced superposed relation, each of said first and second switching means having two stationary positions each having a plurality of contact structures, each of said contact structures having spaced electrically conductive members for receiving a movable contact, each of said first and second switching means having a single movable con-tact carrier having a plurality of contacts which mate with the openings provided by the spaced electrically conductive stationary members of the contact structures, said movable contact carriers pivoting between said two stationary positions when said first and second switches are switched, to engage certain of its electrical contacts with the stationary electrical contacts at one position and break certain of its electrical contacts with the stationary contacts of the other position, first and second energy storage means for pivoting said movable contact carriers on said first and second switching means, respectively, means for storing energy in said first and second energy storage means when it is desired to switch said first and second switching means, first and second latching means associated with each of said first and second switching means respectively, for maintaining the position of said movable contact carriers of said first and second switching means until switching is desired, means for tripping said first latching means to allow said first switching means to switch when said first and second energy storage means have a predetermined amount of energy stored therein, means responsive to the switching of said first switching means for tripping said second latching means and allowing said second switching means to switch a predetermined period of time after said first switching means has switched.

4. A load tap changer for selectively connecting an electrical terminal with a tap on electrical inductive apparatus, comprising tap selector means having first and second contacts adapted for selectively connecting taps on the electrical inductive apparatus, a transfer switch assembly having first and second switching means disposed in spaced superposed relation, each of said first and second switching means having firs-t and second stationary positions each having electrical contacts, with the first and second stationary positions on said first switching means being connected to said first and second contacts on said tap select-or means, respectively, and the first and second stationary positions on said second switching means being electrically connected to first and second stationary positions on said first switching means, each of said first and second switching means having a single movable contact carrier having contacts thereon, said movable contact carriers being pivotally disposed between said two stationary positionson each of said first and second switching means, a

said movable contact carriers pivoting from one stationary position to the other when said first and second switching means are switched to engage certain of its contacts with the contacts at one stationary position and break certain of its contacts with the contacts at the other stationary position, said movable contact carrier of said first switching means being electrically connected to said electrical terminal, resistance means electrically connected between said movable contact carriers of said first and second switching means, first and second energy storage means for pivoting said movable contact carriers on said first and second switching means, respectively, means for storing energy in said first and second energy storage means when it is desired to switch said first and second switching means, first and second latching means disposed on said first and second switching means, respectively, for maintaining the position of said movable contact carriers of said first and second switching means until switching is desired, means for tripping said first latching means to allow said first switching means to switch when said first and sec-0nd energy storage means have a predetermined amount of energy stored therein, means disposed in substantially a vertical manner between said first and second switching means responsive to the switching of said first switching means for tripping said second latching means and allowing said second switching means to switch a predetermined period of time after said first switching means has switched.

5. A load tap changer for selectively connecting an electrical terminal with a predetermined tap on a tapped winding structure, comprising tap selector means having first and second contacts adapted for selectively connecting taps on the tapped winding structure, a transfer switch assembly having first and second switching means having first and second mounting means, respectively, disposed in spaced superposed relation, each of said first and second switching meanshaving first and second stationary positions each having electrical contacts, with the first and second positions on said'first switching means being connected to said first and second contacts on said tap selector 13 means, and the first and second stationary positions on said second switching means being electrically connected to the first and second stationary positions on said first switching means, each of said first and second switching means having a single movable contact carrier having a plurality of electrical contacts and pivotally disposed on said first and second mounting means, said movable contact carriers pivoting between said stationary positions when said first and second switching means are switched, to engage certain of their contacts with the contacts at one stationary position and break certain of their contacts with the contacts at the other position, first and second electrically conductive means insulatingly disposed on said first and second mounting means, respectively, said movable contact carriers of said first and second switching means being electrically connected to said first and second electrically conductive means, said first electrically conductive means being connected to said electrical terminal, resistance means connected between said first and second electrically conductive means, first and second energy storage means for pivoting said movable contact carriers on said first and second mounting means, respectively, means for storing energy in said first and second energy storage means when it is desired to switch said first and second switching means, first and second latching means disposed on said first and second switching means, respectively, for maintaining the position of said movable contact carriers of said first and second switching means until switching is desired, means for tripping said first latching means to allow said first switching means to switch when said first and second energy storage means have a predetermined amount of energy stored therein, means disposed in substantially a vertical manner between said first and second switching means responsive to the switching of said first switching means for tripping said second latching means and allowing said second switching means to switch a predetermined period of time after said first switching means has switched.

6. A transfer switch assembly for a load tap changer comprising, first and second mounting means disposed in spaced superposed relation, first, second, third and fourth stationary contact means each including electrical contacts, said first and second stationary contact means being disposed in spaced relation on said first mounting means, said third and fourth stationary contact means being disposed in spaced relation on said second mounting means, first and second movable contact means each including electrical contacts, said first movable contact means being pivotally disposed on said first mounting means between said first and second stationary contact means, with certain of its electrical contacts engaging the electric-a1 contacts of said first stationary contact means when pivoted in one direction, and certain of its electrical contacts engaging the electrical contacts of said second stationary contact means when pivoted in the other direction, said second movable contact means being pivotally disposed on said second mounting means between said third and fourth stationary contact means, with certain of its electrical contacts engaging the electrical contacts of said third stationary contact means when pivoted in one direction and certain of its electrical contacts engaging the electrical contacts of said fourth stationary contact means when pivoted in the other direction, first and second energy storage means disposed on said first and second mounting means for pivoting said first and second movable cont-act means, respectively, means storing energy in said first and secondenergy storage means when said first and second movable contact means are to be pivoted from one stationary contact means to the other, first and second latching means disposed on said first and second mounting means, respectively, with each latching means including a rotatable latch wheel having notches therein and finger means for engaging predetermined notches on said latch wheel, first and second connecting rod means connected between said first and second latching means and said first and second movable contact means, respectively, said first and second latching means and said first and second connecting rod means maintaining said first and second movable contact means in a predetermined position at one of said stationary contact means while energy is being stored in said first and second energy storage means, means for disengaging said finger means from a first predetermined notch on the latch wheel of said first latching means when the energy stored in said first energy storage means reaches a predetermined magnitude, to allow said first movable contact means to pivot from one of the stationary contact means to the other, the latch Wheel of first latching means being rotated 21 predetermined amount by the movement of said first movable contact means, with said finger means engaging a second predetermined notch when the predetermined rotation of said latch wheel has been completed, means responsive to a predetermined rotation of the latch wheel of said first latching means for disengaging the finger means from a first predetermined notch on the latch wheel of said second latching means, said second movable contact means moving from one stationary contact means to the other when said finger means is disengaged from the latch wheel of said second latching means, the latch wheel of said second latching means rotating a predetermined amount when said second movable contact means moves from one position to the other, with the finger means engaging a second predetermined notch in the latch wheel of said second latching means.

7. A transfer switch assembly for a load tap changer comprising first and second mounting means disposed in spaced superposed relation, first, second, third and fourth stationary contact positions each including electrical contacts, said first and second stationary contact positions being disposed in spaced relation on said first mounting means, said third and fourth stationary contact positions being disposed in spaced relation on said second mounting means, first and second movable contact carriers and contacts, said first movable contact carrier being pivotally disposed on said first mounting means between said first and second stationary contact positions, with certain of its electrical contacts engaging the electrical contacts of said first stationary contact position when'pivotcd in one c direction, and certain of its electrical contacts engaging the electrical contacts at the second stationary contact position when pivoted in the other direction, said second movable contact carrier being pivotally disposed on said second mounting means between said third and fourth stationary contact positions, with certain of its electrical contacts engaging the electrical contacts of said third stationary contact position when pivoted in one direction and certain of its electrical contacts engaging the electrical contacts of said fourth stationary contact position when pivoted in the other direction, first and second energy storage means disposed on said first and second mounting means for pivoting said first and second Lmovable contact carriers, respectively, means storing energy in said first and second energy storing means when said first and second movable contact carriers are to be pivoted from one stationary contact position to the other, first and second latching means disposed on said first and second mounting means, respectively, each including a rotatable latch wheel having notches therein and finger means for engaging predetermined notches on said latch wheel, first and second connecting rod means connected between said first and second latching means and said first and second movable contact carriers, respectively, said first and second latching means and said first and second connecting rod means maintaining said first and second movable contact carriers at one of the stationary contact positions while energy is being stored in said first and second energy storage means, means for disengaging said finger means from a first predetermined notch on the latch wheel of said first latching means when the energy stored in said first energy storage means reaches a predetermined magnitude, to allow said first movable contact carrier to pivot from one of the stationary contact positions to the other, the latch wheel of said first latching means being rotated at predetermined amount by the movement of said first movable contact carrier, with said finger means engaging a second predetermined notch when the predetermined rotation of said latch wheel has been completed, connecting rod means disposed in a substantially vertical manner between the latch wheel of said first latching means and the finger means of said second latching means, said connecting rod means disengaging the finger means from a first predetermined notch on the latch wheel of said second latching means when the latch wheel of said first latching means rotates a predetermined amount, said second movable contact means moving from one stationary contact position to the other when said finger means is disengaged from the latch wheel of said second latching means, the latch wheel of said second latching means rotating a predetermined amount when said second movable contact carrier moves from one position to the other, with the finger means engaging a second predetermined notch in the latch wheel of said second latching means.

8. A transfer switch assembly for a load tap changer comprising first and second mounting means disposed in spaced superposed relation, first, second, third and fourth stationary contact positions each including electrical contacts, said first and second stationary contact positions being disposed in spaced relation on said first mounting means, said third and fourth stationary contact positions being disposed in spaced relation on said second mounting means, first and second movable contact carriers and contacts, said first movable contact carrier being pivotally disposed on said first mounting means between said first and second stationary contact positions, with certain of its electrical contacts engaging the electrical contacts of 7 said first stationary contact position when pivoted in one direction and certain of its electrical contacts engaging the electrical contacts at said second stationary contact position when pivoted in the other direction, said second movable contact carrier being pivotally disposed on said second mounting means between said third and fourth stationary contact positions, with certain of its electrical contacts engaging the electrical contacts of said third stationary contact position when pivoted in one direction and certain of its electrical contacts engaging the electrical contacts of said fourth stationary contact means when pivoted in the opposite direction, drive shaft means disposed on said first mounting means, means for rotating said drive shaft means, a first crank member fixed to said drive shaft means having first and second cam surfaces disposed in spaced relation thereon, first spring means pivotally connected to both said first crank member and said first movable contact carrier, a second crank member pivotally disposed on said second mounting means, second spring means pivotally connected to both said second crank member and said second movable contact carrier, first connecting rod means pivotally connected to both said first and second crank members, which rotates said second crank member when said first crank member is rotated by said drive shaft means, said first and second spring means being actuated by said first and second crank members, respectively, to store energy in said first and second spring means when said drive shaft means is rotated, first latching means including a first rotatable latch wheel having notches therein, and first latching finger means pivotally disposed on said first mounting means, second connecting rod means pivotally connected to both said first latch wheel and said first movable contact carrier, said first latching finger means engaging a first notch on said first latch wheel to maintain said movable contact carrier in a first predetermined position at one of said stationary contact positions, one of the spaced cam surfaces on said first crank member disengaging said first latching finger means from the first notch in said first latch wheel after the energy stored in said first spring means reaches a predetermined magnitude, to allow said first spring means to move said first movable contact carrier from its first predetermined position at one of said stationary contact positions to a second predetermined position at the other stationary contact position, said second connecting rod means rotating said first latch wheel a predetermined distance when said first movable contact carrier is moved, said first latching finger means engaging a second notch in said first latch wheel to maintain said movable contact carrier at said second predetermined position, second latching means including a second rotatable latch wheel having notches therein, and second latching finger means pivotally disposed on said second mounting means, third connecting rod means pivotally connected to both said second latch wheel and said second movable contact carrier, said second latching finger means engaging a first notch on said second latch wheel to maintain said second movable contact carrier in a first predetermined position at one of the stationary contact positions, fourth connecting rod means disposed to be responsive to the movement of said first latch wheel, said fourth connecting rod means disengaging said second latching finger means from said second latch wheel in response to a predetermined amount of rotation of said first latch wheel to allow the stored energy in said second spring means to pivot said second movable contact carrier from its first predetermined position at one of the stationary contact positions to a second predetermined position at the other stationary contact position, said second latch wheel rotating a predetermined amount when said second movable contact carrier pivots to its new predeterminedposition, said second latching finger means engaging a second notch in said second latch .wheel when said second latch wheel completes its predetermined rotation.

9. A transfer switch assembly for a load tap changer comprising first and second mounting means disposed in spaced superposed relation, first, second, third and fourth stationary contact positions each including electrical contacts, said first and second stationary contact positions being disposed in spaced relation on said first mounting means, said third and fourth stationary contact positions being disposed in spaced relation on said second mounting means, first and second movable contact carriers and contacts, said first movable contact carrier being pivotally disposed on said first mounting means between said first and second stationary contact positions, said second movable contact carrier being pivotally disposed on said second mounting means between said third and fourth stationary contact positions, drive shaft means disposed on said first mounting means, means for rotating said drive shaft means, a first crank member fixed to said drive shaft means, first spring means pivotally connected to both said first crank member and said first movable contact carrier, a second crank member pivotally disposed on said second mounting means, second spring means pivotally connected to both said second crank member and said second movable contact carrier, first connecting rod means pivotally connected in a substantially vertical manner between said first and second crank members which rotates said second crank member when said first crank member is rotated by said drive shaft means, said first and second spring means being actuated by said first and second crank members, respectively, to store energy in said first and second spring means when said drive shaft means is rotated, first latching means including a first rotatable latch Wheel, and first and second latching fingers pivotally disposed on said first mounting means, second connecting rod means pivotally connected to both said first latch wheel and said first movable contact carrier, one of said first and second latching fingers engaging a first predetermined notch on said first latch wheel to maintain said first movable contact carrier in a first predetermined position at one of said stationary contact positions, said first crank member disengaging said engaged latch finger from said first latch wheel after the energy stored in said first spring means reaches a predetermined magnitude, to allow said first spring means to move said first movable contact carrier from one of said stationary contact positions to the other, said second connecting rod means rotating said first latch wheel a predetermined amount when said first movable contact carrier is moved, with said remaining latching finger engaging a second predetermined notch in said first latch wheel to maintain said first movable contact carrier at its new position, second latching means including a second rotatable latch wheel having notches therein, and third and fourth latching fingers pivotally disposed on said second mounting means, third connecting rod means pivotally connected to both said second latch wheel and said second movable contact carrier, one of said third and fourth latching fingers engaging a first predetermined notch on said second latch wheel to maintain said second movable contact carrier at one of said stationary contact positions, fourth connecting rod means disposed in a substantially vertical manner between said first latch wheel andsaid third and fourth latching fingers, said fourth connecting rod means disengaging the latching finger that is engaging said second latch wheel when said first latch wheel rotates a predetermined amount, to allow the stored energy in said second spring means to pivot said second movable contact carrier from one stationary contact position to the other, said second latch wheel rotating a predetermined amount when said second movable contact carrier pivots to its new position, with the remaining latching finger engaging a second predetermined notch in said second latch wheel, when said second latch wheel completes its predetermined rotation.

10. A transfer switch assembly for a load tap changer comprising first and second mounting means disposed in spaced superposed relation, first, second, third and fourth stationary contact positions each including electrical contacts, said first and second stationary contact positions being disposed in spaced relation on said first mounting means, said third and fourth stationary contact positions being disposed in spaced relation on said second mounting means, first and second movable contact carriers and contacts, said first movable contact carn'er being pivotally disposed on said first mounting means between saidfirst and stationary contact positions, said second ggontact carrier being pivotally disposed on said secohc L gounting means between said third and fourth stationary contact positions, drive shaft means disposed on said first mounting means, means rotating said drive shaft means, a first crank member fixed to said drive shaft means having first, second, third and fourth cam surfaces disposed in spaced relation thereon, first spring means pivotally connected to both said crank member and said first movable contact carrier, a second crank member pivotally disposed on said second mounting means having first and second cam surfaces thereon, second spring means pivotally connected to both said second crank member and said second movable contact carrier, first connecting rod means pivotally connected to both said first and second crank members which rotates said second crank member when said first crank member is rotated by said drive shaft means, said first and second spring means being actuated by said first and second crank members, respectively, to store energy in said first and second spring means when said drive shaft means is rotated, first latching means including a first rotatable latch Wheel having notches therein and first latching finger means, second connecting rod means pivotally connected to both said first latch wheel and said first movable cont-act carrier, said first latching finger means engaging a first predetermined notch on said first latch wheel to main said said first movable contact carrier at one of said stationary contact positions, one of said first and second cam surfaces on said first crank member disengaging said first latching finger means from said first latch wheel after the energy stored in said first spring means reaches a predetermined magnitude, to allow said first spring means to pivot said first movable contact carrier from one stationary contact position to the other, said second connecting rod means rotating said first latch wheel a predetermined amount when said first movable contact carrier is pivoted, with said first latching finger means engaging a second predetermined notch in said first latch wheel to maintain said first movable contact carrier at the nevi? stationary contact position, second latching means including a second rotatable latch wheel having notches therein and second latching finger means, third connecting rod means pivotally connected to both said second latch wheel and said second movable contact carrier, said second latching finger means engaging a first predetermined notch on said second latch wheel to maintain said second movable contact carrier at one of said stationary contact positions, fourth connecting rod means disposed in a substantially vertical manner between said first latch wheel andsaid second latching finger means, said fourth connecting rod means disengaging said second latching finger means from said second latch wheel when said first latch wheel rotates a predetermined amount, to allow the stored energy in said second spring means to pivot said second movable contact carrier from one of the stationary contact positions to the other, said second latch wheel rotating a predetermined amount when said second movable contact carrier pivots to its new position, said second latching finger means engaging a second predetermind notch in said second latch wheel when said second latch wheel completes its predetermined rotation, third and fourth crank members each having a cam surface thereon and pivotally disposed on said first and second mounting means, respectively, means mechanically linking said third crank member with said second connecting rod means, means mechanically linking said fourth crank member with said third connecting rod means, one of said third and fourth cam-s on said first crank member engaging the cam surface on said third crank member when said first movable contact carrier fails to pivot a predetermined amount, to mechanically force said first movable contact carrier and first latch wheel to complete their travel, one of the first and second cams on said second crank member engaging the cam surface on said fourth crank member when the second movable contact carrier fails to pivot a predeterminedamount, to mechanically force said second movable, contact carrier and second latch wheel to complete their travel.

No references cited.

ROBERT K. SCHAEFER, Primary Examiner. J. R. SCOTT, Assistant Examiner. 

1. A TRANSFER SWITCH ASSEMBLY FOR A LOAD TAP CHANGER COMPRISING FIRST AND SECOND SWITCHING MEANS DISPOSED IN SPACED SUPERPOSED RELATION, EACH OF SAID FIRST AND SECOND SWITCHING MEANS HAVING TWO STATIONARY POSITIONS EACH HAVING ELECTRICAL CONTACTS, AND A SINGLE MOVABLE CONTACT CARRIER HAVING CONTACTS, SAID MOVABLE CONTACT CARRIER BEING PIVOTALLY DISPOSED BETWEEN SAID TWO STATIONARY POSITIONS, FIRST AND SECOND ENERGY STORAGE MEANS FOR PIVOTING SAID MOVABLE CONTACT CARRIERS OF SAID FIRST AND SECOND SWITCHING MEANS, RESPECTIVELY, MEANS FOR STORING ENERGY IN SAID FIRST AND SECOND ENERGY STORAGE MEANS WHEN IT IS DESIRED TO SWITCH THE MOVABLE CONTACT CARRIERS OF SAID FIRST AND SECOND SWITCHING MEANS FROM ONE STATIONARY CONTACT POSITION TO THE OTHER, FIRST AND SECOND LATCHING MEANS ASSOCIATED WITH EACH OF SAID FIRST AND SECOND SWITCHING MEANS, RESPECTIVELY, FOR MAINTAINING THE POSITION OF SAID MOVABLE CONTACT CARRIERS OF SAID FIRST AND SECOND SWITCHING MEANS UNTIL SWITCHING IS DESIRED, MEANS TRIPPING SAID FIRST LATCHING MEANS TO ALLOW SAID FIRST SWITCHING MEANS TO SWITCH WHEN SAID FIRST AND SECOND ENERGY STORAGE MEANS HAVE A PREDETERMINED AMOUNT STORED THEREIN, MEANS RESPONSIVE TO 